Electronic marker for cathode-ray indicator tubes



April 1952 R. R. SCOVILLE 5 4,0 78

ELECTRONIC MARKER FOR CATHODE-RAY INDiCATOR TUBES Filed March 50, 1946 FIG. 4 FIG. 3

RA NGE 6O 30 I0 0 I0 30 6O AZIMUTl-l FREQ. MLIZER FIG. 5 FIG. 2

W E s g g s 60 30 IO 0 IO 30 60 S 60 30 l0 'IO 30 60 & ANGLE 6 DEGREES & ANGLE 9 DEGREES a E 8 o //v VENTOR R R. SCOV/LLE A770 NE) Patented Apr. 22, 1952 2,594,078

ATE NT Q F QE 1 smcrnoniamnisn CATHODE-RAY INDIQA'EOR Ray B. Scoyille, Glendale, Calif., assignorto Bell Tel ephoneTI abora ories, Incorporated, New Y ork,N Y., a e1 oration oijNew York 5 Serial-N9; Ga es; (Ch 3 .37%

whims:

2- fiup ets et en r duc a e s. f. n: eguf verti'cal straight line patterns; each o f whlchis slightly displa ced in a horizontal v} directionwithrespectto the pattern immediately pre- 5 ceding, "Since the vertical s'canningmotioni of the electron beam is rapid, the successivepat terns, closely spaced, and the intensity of the be regulated to a low. intensity by means -of a control grid bias, the fluorescent screen 'appears 10 tothe eye to glow dimly with a uniform light; Reflected signals returning from objects in 'th'e field through the conventional signal receiving 1 This relates in general. to, e circuits and in particular tojj electronic calibration lines on cathode ray: indicator tubel" Broadly, thefobject of thi's inventionis top Q- vide a superior technique for corfr'] tronic calibration marks on acat cator screenr with preselected 150s i mmberl A more specific object of this invention i in the oscilloscope thuscausing spots of relatively 4 Y high luminosityto appear on the screen which f elm /of h; sition of its '1 fie represent; the locations of detected Qbje cts'in the screen, ra' no azimuth.

"Additional objects may be "As pointed. out. in' the above-stated objects, in accuratelylocating bodies in space or determin ingfdir'ections, the further problem arisesof providing suitable mean s for calibrating the'oscilloscope screen in terms of preselected antenna sea ningangles' In place of thecompleii prior aft circuits developed for the purpose of pro-- J diifiinfg' electronic calibration lines on the oathod'e r jay, indicator screen, the present invention envisions a simple modification of the horizontal sweep circuit. o f the system described in the foregoi paragraph This comprises introducing mean in the oscilloscope control circuits to mome 1y alter'the' progress of the rapid scandetermine thefazimuth position. flab dy system it is desired to ha be in trace a pattern which rep ranges of detected. objects a in zi ut ne on m h n s l' i h el e m n??? PP l CiQ about this result is as follows p the cycle oi the scanning antenna or m a t too i scope toand fro motion on thescree and sense of which 'cor fspdnd sweep of the antenna beam' circuit of the oscilloscope 1s of volt e wh c a "'i azimuth antenna drive. I circular rheostat connected a rect current sourceof power" mechanically coupled to 'th shaft, the varying voltage out impressed ac'ros's'the vertical la loscope. Thus, during thec an y e he ho W? varies cyclically from a maximum n'e maximum positive value and vice vers eous yhe e is nress tal plates'of the oscillosc frequency of oscillation w he' ee f ver tiqn 6i n. system and which is inanyi'hu (ll; frequency of the horizont Thus, during each cyclej't driven substantially progressi th .11 qua y-m m bqdyi 4 New? w th mb d m nt of the present invention, elements of high resistance are the fwhich,in combination with a constant l1 fiou r gce, furnishes the horizontal sweep across one pair of oscilloscope deflecting By; rtue ot this device, the horizontal tage, instead of increasing or' degr es: or" ly' inaccordance with the antenna 'in 'synchronism with the rotating passes 'over the junction'at which elements are inserted. The hori zonalfrate" oi] movement of "the vertically s fining luini ous spot' on the oscilloscope screen acceleratedateach'such peja dark gap or line to a pease ive yertical scanning tracesi "This attern ot dark line vertical calihan correspond to designated in azimuth. h e with another embodiment, elementso low resistance are "inserted at" spaces direction across the in H lshnthe'rheostatbfthdhbriZGntal "sweep the movement of the sea ni cir Whenever the synchronously meme 7 k J I rhe tat wiperfco'mes in contact with such'a low cy g zliqgal rate in the vertiea l; resistf' r'iceelement the horizontal sweep voltage causes the luminous 'spot to vertically'scan the outputfisinomentariiy held constant whereby the apparatus modify the potential on the control grid;

ins ted at preselected points on the circular rises sharply whenever the rheos't'at 3 luminous spot is constrained to trace repeatedly for a short time interval the same vertical path on the oscilloscope screen thus marking the said position by means of a relatively bright vertical marker line.

A better understanding of the present invention may be had from a study of the detailed description as set forth hereinafter and the accompanying drawings, in which:

Fig. 1 shows an object locating and direction finding system such as disclosed in Patent 2,581,- 847, issued January 8, 1952, by L. Espenschied and J. G. Chaifee, which has been modified in accordance with the present invention by thev introduction at spaced intervals of elements of relatively high resistance in the rheostat of the horizontal sweep producing circuit;

Fig. 2 shows a plot of the horizontal sweep voltage in the receiver oscilloscope against the azimuth angle of the antenna of Fig. 1;

Fig. 3 shows the series of azimuth marker lines' which appear on the oscilloscope screen in the plot of range against azimuth in the system of Fig. 1;

Fig. 4 shows an alternative embodiment of the.

excepting the horizontal sweep circuit of the' cathode ray oscilloscopewhich is modified in accordance with the present invention, are substantially similar to corresponding components of the system disclosed in Patent 2,581,847 to L. Espenschied and J. G. Chaifee.

The system of Fig. 1 comprises a-pair of aligned directional transmitting and receiving electromagnetic radiators I and 2 respectively, which, may comprise directional horns as shown or. one of the several types of directional antenna arrays These are mounted in j well known in the art. I a housing 3 which is adapted .to be rotated by means of the antenna drive 4 operating through the gears 5 on the shaftii.

The transmitting horri l is connected through contact 9' attached to the slip ring 9 and brush 8 riding thereon to the circuit of the frequency modulating transmitter entitled A Terrain Clearance Indicator by L.

Espenschied and R. C. Newhouse, Bell System. Technical Journal, volume XVIII, January 1939. The receiving horn 2 whose function it is to receive freqency modulated signals reflected from objects in the field is connected through contact I2 rigidly attached to the slipring i2 and the brush ll riding thereon to the frequency modu-. lation receiving circuit l3. The frequency modulation receiver i3 is adapted to directly receive a reduced output component of the signal transmitted from the frequency modulating transmitter ll] through a circuit which includes a high.

impedance element l4. The difference or beat frequency resulting from the two input frequencies simultaneously impressed on the receiver l3, namely, the outgoing signal conducted directly from the transmitter [0 through the impedance l4, and the signal reflected from an object in the field, and received through the receiving antenl0, the operation of. which is substantially as described in a paper,

na 2, is passed through a conventional amplifier l5 to the circuit of the variable frequency analyzer It. This apparatus is driven by means of the motor l! acting through the gears 18 on the shaft '19 to select continuously changing frequencies which sweep back and forth over a range corresponding to the range of distances over which the radio object locating and direction finding system is adapted to operate. Thus, a signal from the receiver l3, after selection by the variable frequency analyzer It is led through the rectifying circuit 29 and impressed across the high resistance 22 which is connected between the circuit of the control grid 23 and the cathode 24 of the cathode ray oscilloscope 25. The bias imposed on the electron beam of the cathode ray oscilloscope 25 by means of the negative biasing battery 26,.is thus reduced momentarily, therebycausing after.

The cathode ray oscilloscope 25, which is a conventional type, includes intensifying and. focusing electrodes 27 and 28 and horizontal and vertical pairs of electrostatic deflecting plates 29 and 30 whose. function it is to control the position of the luminous spot on the fluorescent screen 32 in accordance with the azimuth position of the scanning antenna l, 2 and the rangingoperation of the ,object locating and direction finding system, as explained hereinafter.

The rapid vertical oscillatory motion of the luminous spot on the cathode ray screen 32, the rate of which corresponds to the range of operation over which the object locating and direction finding. system is adapted to receive reflected signals from the objects in the field, may be under control of a circuit of the following type.

One of the pair of horizontal plates 29 which controls thevertical sweep of the electron beam is connected to ground while the other plate is connected through a circuit which includes the adjustable contact 34, the positive potential source 35, .the brush 36 riding on the slip ing 31, the conducting shaft i9, and the wiper 33 riding on the circular rheostat 39 which is connectedacross the direct current power source 40. The'wiper 38 is adapted to be driven by the motor ll operating through, the gears i8 and the shaft I9, 19', to move around the circular rheostat 39 so that an oscillatory voltage which varies synchronously with the frequency sweep of the variable frequency analyzer IB is impressed across the horizontal plates 29.

A circuit designed to control the horizontal sweep of the oscilloscope beam in synchronism with the azimuth sweep of the scanning antenna in a sys tem as described may have the following components:.

The. vertical plates 30, which control the horizontal sweep of theelectron beam on the fluorescent screen 32, are connected by means of a circuit which includes the lead wires 42, and the brushes 44 and 45 riding on the slip rings 46 and I 41 respectively, to the respective wipers 48 and trace on the indicator screen 32, the adjustable 5 antic-ohm resistors 55 and 56V are included in. the circuit of the rheostat 5,0.

In accordance with the present invention, azi: muth marker lines are produced electronically on the screen 32 of the cathode ray oscilloscope. by the following modification of the horizontal sweep circuit. Bunched resistance elements 5! and 5,8 are inserted at. spaced intervals in the winding of the voltage dividing circuit 50 in such a manner as to secure sharp rises in the output voltage across the lead wires 42 at designated positions of the scanning antenna le-2, ior example, the broadside position, designated as degrees, and :10, 30 and 60 degree in azimuth. It is important that the junction wires 60, whereby the resistance elements and 5 8 are inserted in the circuit of the rheostat 50, shall be closely enough spaced in accordance with the width of the contact brush 49 that some part of the brush is continuously in contact with the rheostat winding. The brush 4'9 does not come directly in contact with the resistance elements 51 and 58,

Assuming that the scanning antenna array l-.-2 moves horizontally to and fro through an angular sector of 180 degrees, the brushes and 49 are thereby caused to move around in contact with the circular rheostat 50 so that the output voltage impressed on the attenuating voltage divider 58 is varied from zero when the antenna array 5-2 i in oadside pos tion to a ma mum positiv or n ative value wh n the a a is in one of the positions at right angles to the broadside position. In the apparatus or Big. 1, in which the rheosta-t 5e connected across the series connected ZOO-volt batteries 52 and 53, the maximum positive or negative output voltage realized is approximately 750 volts. as the antenna array !-2 moves back and forth through a horizontal are of 180 degrees, the vertical plates as assume alternately positive and negative potentials, the direction. of the electrostatic field being progressively reversed between them, thus sweeping the electron beam of the cathode ray oscilloscope 25 slowly back and forth across the fluorescent screen 32,. a conventional cathode ray oscilloscope such described, a typical value for the potential difierence between the plates 33 for maximum sweep of the electron beam is 490 ,volts. It is therefore necessary to introduce the attenuating voltage divider 59 into the circuit in order to reduce the maximum output voltageacross the rheostat 50 to this value.

In the course or" the azimuth scanning-motion of the antenna array l-.2, whenever the brush 49 passes over one of the junctions 60 on the rheostat 5! the output voltage impressedon the plates as rises sharply, :as shown graphically Fig. 2, in which the output voltage across the leads &2 is plotted against the azimuth angle of the antenna.

As described hereinbefore, the rapid vertical oscillations imposed on the electron beam of the oscilloscope 25 by the horizontal plates 29 are under control of the rheostat 39 connected across the constant potential source 40, the wiper 38 being driven by the motor I! which also drives the variable frequency analyzer [6. The fre* quen y orthe vertical osc llat ons o the e ect o beam of the cathode ray tube are therefore determined in accordance with therange over-which the radio object locating and direction finding system described herein is adaptedlto operate.

When the horizo al mot on impo d on th electron bea by the ver icalznlates 30 rl sr imerposed on the vertical motion imposed on the bean;

by the horizontal plates 29, a series of yert scanning lines is progressively traced on the screen, the vertical motion or" the electron beam being so rapid and the intensity of the beam so regulated that the screen gives the appearance of a uniform glow if the scanning lines are uni; formly spaced. However, the presence oi" the bunched resistance elements 5'! and 58 in the azimuth voltage divider 5e, brings about sharp rises in the horizontal sweep voltage at gigs: ignated points, as described above, thereby causing appreciable gaps between successive ver scanning lines traced on the screen 32 which A the appearance of dark lines. Figure 3 of i drawings shows the pattern of azimuth marlger lines appearing on the screen in a plotting, of range against antenna azimuth angle whenthe bunched resistance elements 51 and 53 are in positions corresponding to 0 degrees, :10 de? grees, 30 degrees and 60 degrees in azimuth.

In, the circuit of Fig. lyassume that the total resistance of the circula' rheostat 5i: is 50,000 ohms, and that the horizontal extent of the pat: tern on the creen 32 of the cathode ray oscilloscope 25 is 1% inches. Then a typical value tor the inserted resistance elements 51, in order to produce dark calibration lines having a width of 12 mils on the screen 32 at azimuth angles 0 ole.- grees and i30 degrees, is 770 ohms. If it is tie-.- sired to have marker lines at :10 degrees and :60 degree which are 6 mils wide, the resistance 58 inserted at these points will be approximately 385 ohms.

A variation of the present invention is shown in Fig. 4 of the drawings, in which the high re; sistance elements 5} and 58 of the rheostat 50 are replaced with low resistance elements 51A and 58A which, however, are so positioned that the contact brushes MA and dQA pass directly and in contact with them when moving around the rheoe stat 50. Moreover, the arcuate extent of each of the elements 51A and 58A relative to the width of the brushes 68A and @SA is such thatbrushes passing thereover maintain contact with these elements exclusively for a short but appreciable interval. The other components of the rheost at. 50 together with the batteries 53A and 52A are similar in function and structure to corresponds ing components described above with reference to Fig. 1 of the drawings; and the leads d2 of the circuit of Fig. 4 may be assumed to be connected across the voltage divider 59 in the same manner as in the system of Fig. 1. As the brushes 48A and 49A move over a pair of corresponding low resistance elements 57A or 58A making contact therewith, the voltage output across the leads .42, which is impressed on the voltage divider 59,.cloes not change appreciably until the brushes reach the ends of the elements. Fig. 5 of the drawings shows a plot of the output voltage produced by the system of Fig. 4 across the voltage dividerjfl against the azimuth scanning angle of the an-- tenna array 1-2.

,Instead of the dark line system of azimuth-calibration marks, shown in Fig. '3 of the drawings and produced by the system described with ref erence to Fig. 1, the modified system disclosed in Fig. f1: produces a series of bright line calibrat cmna k As explained hereinbefore, the electron beam vertically scans the fluorescent screen 32- unde r control of the rapidly oscillatingvertical sweep c tase superp se n t e p es ss rel im a n and decreasin horizon al s ee delicac- During intervals in which the brushes 48A and 49A are moving over one of the pairs of low resistance elements 51A or 58A, the luminou spot tends to move repeatedly over the same vertical scanning line of the screen 32, thereby causing a relatively bright line to appear. A system of bright azimuth lines is thus produced on the screen 32, the positions of which are correlated with the azimuth positions of the elements 51A and 58A and hence desired azimuth positions of the antenna l--2.

Although the present invention has been described as adapted for use in an object location and direction finding system employing electromagnetic waves in the form of frequency modulated signals, it is equally applicable to radio ranging and directional systems employing electromagnetic pulses, or other types of electromagnetic signals known in the art. The present invention is not limited to the use of the particular apparatus or system of the present disclosure.

What is claimed is:

1. In a radio system which comprises in combination transmitting means, receiving means, an antenna connected to said transmitting and said receiving means, said antenna having a driving means attached thereto through a drive shaft, a cathode ray tube connected to said receiving means, said tube having a source of a beam of electrons, an indicator screen disposed in the path of said beam, and a sweep circuit connected to control the motion of said beam on said screen, a source of power, and a voltage divider connected between said source of power and said sweep circuit, said voltage divider comprising a resistor and a contact which moves on said re- .sistor in synchronism with the movement of said .antenna drive shaft, means for producing electronic marker lines on said indicator screen which comprise irregularitie in the resistance characteristic at spaced intervals on the resistor of said voltage divider.

2. A system as characterized in claim 1 in which said irregularities comprise elements having relatively higher resistance per unit length than that of intervening portions of said voltage divider.

3. A system as characterized in claim 1 in -which said irregularities comprise elements havfing relatively lower resistance per unit length than that of intervening portions of said voltage divider.

4. A radio system comprising in combination a cathode ray tube having a source of a beam of electrons, an indicator screen disposed in the path of said beam, and a sweep producing circuit connected to control the motion of said beam on said screen, a cyclically moving member, a source of power, means comprising a voltage divider under control of said cyclically moving member and connected to said sweep producing circuit and said source of power to vary the position of the indication produced by said beam on the indicating screen in accordance with the position of said'cyclically moving member, and means comprising irregularitie in the resistance of said voltage divider to produce electronic calibration marks on said indicator screen.

5. In a radio system including a scanning antenna, an antenna driving means, and a cathode -ray indicator tube having a source of a beam of electrons, an indicator screen disposed in the path of said beam, and a sweep circuit connected to control the motion of said beam on said screen, a source of power, a voltage divider, the

input of said voltage divider connected across said source of power, said voltage divider mechanically coupled to said antenna drive and having an output which varies in accordance with the position of said antenna, the output of said voltage divider electrically connected across said sweep circuit, and means comprising irregularities in the resistance of said voltage divider for producing electronic markers on said indicator screen.

6. In combination with a cyclically moving body, an oscilloscopic system including a oath ode ray tube having a luminescent screen, and means for producing a ray of energy directed to impinge on said screen, a first ray deflecting means comprising a mechanism repeatedly operative through a cycle of movement substantially in synchronism with the cyclical movement of said body for moving the ray in one direction across said screen a second ray deflecting means for simultaneously moving said ray at a many times greater cyclical rate in another direction across said screen, and means comprising irregularities'at the same pre-selected positions in each operative cycle of said first ray deflecting means for momentarily altering the rate of movement of said ray in said one direction whenever said body assumes said preselected positions in its cycleof movement, whereby a correspondence is established between said positions and particular positions on said screen.

'7. A system comprising in combination a signal receiver including scanning means operative through a repetitive cycle to continually change the direction of radiant action of said receiver whereby a preselected area is continually scanned to locate signals, a cathode-ray indicator tube connected to said receiver for indicating the location of said signals, said tube including a luminescent screen, means for producing a ray of energy directed to impinge on said screen, a first ray deflecting means comprising a mechanism operative through a cycle of movement substantially in synchronism with said scannin means for repeatedly moving the ray at a smooth rate of speed in a first direction across said screen, and a second ray deflecting means for repeatedly moving the ray in a second direction across said screen, the motion of said ray in said second direction having a cyclical rate which is many times greater than the cyclical rate of the motion of said ray in said first direction, and means comprising irregularities at the same preselected positions in each operative cycle of said ray deflecting means for momentarily altering the smooth rate of speed of said ray in said first direction whenever said scanning means assumes said preselected positions in its cycle, whereby a correspondence is established between said positions and particular positions on said screen.

RAY R. SCOVILLE.

REFEEENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

